Messages in this thread | | | Subject | Re: [PATCH 4.13 09/36] PM / QoS: Fix device resume latency PM QoS | From | "Rafael J. Wysocki" <> | Date | Tue, 7 Nov 2017 01:51:02 +0100 |
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On 11/6/2017 10:12 AM, Greg Kroah-Hartman wrote: > 4.13-stable review patch. If anyone has any objections, please let me know.
Please drop this from the -stable queue, it has been reverted from the mainline.
Thanks,
Rafael
> ------------------ > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > commit 0cc2b4e5a020fc7f4d1795741c116c983e9467d7 upstream. > > The special value of 0 for device resume latency PM QoS means > "no restriction", but there are two problems with that. > > First, device resume latency PM QoS requests with 0 as the > value are always put in front of requests with positive > values in the priority lists used internally by the PM QoS > framework, causing 0 to be chosen as an effective constraint > value. However, that 0 is then interpreted as "no restriction" > effectively overriding the other requests with specific > restrictions which is incorrect. > > Second, the users of device resume latency PM QoS have no > way to specify that *any* resume latency at all should be > avoided, which is an artificial limitation in general. > > To address these issues, modify device resume latency PM QoS to > use S32_MAX as the "no constraint" value and 0 as the "no > latency at all" one and rework its users (the cpuidle menu > governor, the genpd QoS governor and the runtime PM framework) > to follow these changes. > > Also add a special "n/a" value to the corresponding user space I/F > to allow user space to indicate that it cannot accept any resume > latencies at all for the given device. > > Fixes: 85dc0b8a4019 (PM / QoS: Make it possible to expose PM QoS latency constraints) > Link: https://bugzilla.kernel.org/show_bug.cgi?id=197323 > Reported-by: Reinette Chatre <reinette.chatre@intel.com> > Tested-by: Reinette Chatre <reinette.chatre@intel.com> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Acked-by: Alex Shi <alex.shi@linaro.org> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > --- > Documentation/ABI/testing/sysfs-devices-power | 4 + > drivers/base/cpu.c | 3 - > drivers/base/power/domain_governor.c | 53 ++++++++++++++------------ > drivers/base/power/qos.c | 2 > drivers/base/power/runtime.c | 2 > drivers/base/power/sysfs.c | 25 ++++++++++-- > drivers/cpuidle/governors/menu.c | 4 - > include/linux/pm_qos.h | 5 +- > 8 files changed, 63 insertions(+), 35 deletions(-) > > --- a/Documentation/ABI/testing/sysfs-devices-power > +++ b/Documentation/ABI/testing/sysfs-devices-power > @@ -211,7 +211,9 @@ Description: > device, after it has been suspended at run time, from a resume > request to the moment the device will be ready to process I/O, > in microseconds. If it is equal to 0, however, this means that > - the PM QoS resume latency may be arbitrary. > + the PM QoS resume latency may be arbitrary and the special value > + "n/a" means that user space cannot accept any resume latency at > + all for the given device. > > Not all drivers support this attribute. If it isn't supported, > it is not present. > --- a/drivers/base/cpu.c > +++ b/drivers/base/cpu.c > @@ -377,7 +377,8 @@ int register_cpu(struct cpu *cpu, int nu > > per_cpu(cpu_sys_devices, num) = &cpu->dev; > register_cpu_under_node(num, cpu_to_node(num)); > - dev_pm_qos_expose_latency_limit(&cpu->dev, 0); > + dev_pm_qos_expose_latency_limit(&cpu->dev, > + PM_QOS_RESUME_LATENCY_NO_CONSTRAINT); > > return 0; > } > --- a/drivers/base/power/domain_governor.c > +++ b/drivers/base/power/domain_governor.c > @@ -14,23 +14,20 @@ > static int dev_update_qos_constraint(struct device *dev, void *data) > { > s64 *constraint_ns_p = data; > - s32 constraint_ns = -1; > + s64 constraint_ns = -1; > > if (dev->power.subsys_data && dev->power.subsys_data->domain_data) > constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns; > > - if (constraint_ns < 0) { > + if (constraint_ns < 0) > constraint_ns = dev_pm_qos_read_value(dev); > - constraint_ns *= NSEC_PER_USEC; > - } > - if (constraint_ns == 0) > + > + if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT) > return 0; > > - /* > - * constraint_ns cannot be negative here, because the device has been > - * suspended. > - */ > - if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0) > + constraint_ns *= NSEC_PER_USEC; > + > + if (constraint_ns < *constraint_ns_p || *constraint_ns_p < 0) > *constraint_ns_p = constraint_ns; > > return 0; > @@ -63,10 +60,14 @@ static bool default_suspend_ok(struct de > > spin_unlock_irqrestore(&dev->power.lock, flags); > > - if (constraint_ns < 0) > + if (constraint_ns == 0) > return false; > > - constraint_ns *= NSEC_PER_USEC; > + if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT) > + constraint_ns = -1; > + else > + constraint_ns *= NSEC_PER_USEC; > + > /* > * We can walk the children without any additional locking, because > * they all have been suspended at this point and their > @@ -76,14 +77,19 @@ static bool default_suspend_ok(struct de > device_for_each_child(dev, &constraint_ns, > dev_update_qos_constraint); > > - if (constraint_ns > 0) { > - constraint_ns -= td->suspend_latency_ns + > - td->resume_latency_ns; > - if (constraint_ns == 0) > - return false; > + if (constraint_ns < 0) { > + /* The children have no constraints. */ > + td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT; > + td->cached_suspend_ok = true; > + } else { > + constraint_ns -= td->suspend_latency_ns + td->resume_latency_ns; > + if (constraint_ns > 0) { > + td->effective_constraint_ns = constraint_ns; > + td->cached_suspend_ok = true; > + } else { > + td->effective_constraint_ns = 0; > + } > } > - td->effective_constraint_ns = constraint_ns; > - td->cached_suspend_ok = constraint_ns >= 0; > > /* > * The children have been suspended already, so we don't need to take > @@ -145,13 +151,14 @@ static bool __default_power_down_ok(stru > td = &to_gpd_data(pdd)->td; > constraint_ns = td->effective_constraint_ns; > /* default_suspend_ok() need not be called before us. */ > - if (constraint_ns < 0) { > + if (constraint_ns < 0) > constraint_ns = dev_pm_qos_read_value(pdd->dev); > - constraint_ns *= NSEC_PER_USEC; > - } > - if (constraint_ns == 0) > + > + if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT) > continue; > > + constraint_ns *= NSEC_PER_USEC; > + > /* > * constraint_ns cannot be negative here, because the device has > * been suspended. > --- a/drivers/base/power/qos.c > +++ b/drivers/base/power/qos.c > @@ -189,7 +189,7 @@ static int dev_pm_qos_constraints_alloca > plist_head_init(&c->list); > c->target_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE; > c->default_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE; > - c->no_constraint_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE; > + c->no_constraint_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT; > c->type = PM_QOS_MIN; > c->notifiers = n; > > --- a/drivers/base/power/runtime.c > +++ b/drivers/base/power/runtime.c > @@ -253,7 +253,7 @@ static int rpm_check_suspend_allowed(str > || (dev->power.request_pending > && dev->power.request == RPM_REQ_RESUME)) > retval = -EAGAIN; > - else if (__dev_pm_qos_read_value(dev) < 0) > + else if (__dev_pm_qos_read_value(dev) == 0) > retval = -EPERM; > else if (dev->power.runtime_status == RPM_SUSPENDED) > retval = 1; > --- a/drivers/base/power/sysfs.c > +++ b/drivers/base/power/sysfs.c > @@ -218,7 +218,14 @@ static ssize_t pm_qos_resume_latency_sho > struct device_attribute *attr, > char *buf) > { > - return sprintf(buf, "%d\n", dev_pm_qos_requested_resume_latency(dev)); > + s32 value = dev_pm_qos_requested_resume_latency(dev); > + > + if (value == 0) > + return sprintf(buf, "n/a\n"); > + else if (value == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT) > + value = 0; > + > + return sprintf(buf, "%d\n", value); > } > > static ssize_t pm_qos_resume_latency_store(struct device *dev, > @@ -228,11 +235,21 @@ static ssize_t pm_qos_resume_latency_sto > s32 value; > int ret; > > - if (kstrtos32(buf, 0, &value)) > - return -EINVAL; > + if (!kstrtos32(buf, 0, &value)) { > + /* > + * Prevent users from writing negative or "no constraint" values > + * directly. > + */ > + if (value < 0 || value == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT) > + return -EINVAL; > > - if (value < 0) > + if (value == 0) > + value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT; > + } else if (!strcmp(buf, "n/a") || !strcmp(buf, "n/a\n")) { > + value = 0; > + } else { > return -EINVAL; > + } > > ret = dev_pm_qos_update_request(dev->power.qos->resume_latency_req, > value); > --- a/drivers/cpuidle/governors/menu.c > +++ b/drivers/cpuidle/governors/menu.c > @@ -298,8 +298,8 @@ static int menu_select(struct cpuidle_dr > data->needs_update = 0; > } > > - /* resume_latency is 0 means no restriction */ > - if (resume_latency && resume_latency < latency_req) > + if (resume_latency < latency_req && > + resume_latency != PM_QOS_RESUME_LATENCY_NO_CONSTRAINT) > latency_req = resume_latency; > > /* Special case when user has set very strict latency requirement */ > --- a/include/linux/pm_qos.h > +++ b/include/linux/pm_qos.h > @@ -27,16 +27,17 @@ enum pm_qos_flags_status { > PM_QOS_FLAGS_ALL, > }; > > -#define PM_QOS_DEFAULT_VALUE -1 > +#define PM_QOS_DEFAULT_VALUE (-1) > +#define PM_QOS_LATENCY_ANY S32_MAX > > #define PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE (2000 * USEC_PER_SEC) > #define PM_QOS_NETWORK_LAT_DEFAULT_VALUE (2000 * USEC_PER_SEC) > #define PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE 0 > #define PM_QOS_MEMORY_BANDWIDTH_DEFAULT_VALUE 0 > #define PM_QOS_RESUME_LATENCY_DEFAULT_VALUE 0 > +#define PM_QOS_RESUME_LATENCY_NO_CONSTRAINT PM_QOS_LATENCY_ANY > #define PM_QOS_LATENCY_TOLERANCE_DEFAULT_VALUE 0 > #define PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT (-1) > -#define PM_QOS_LATENCY_ANY ((s32)(~(__u32)0 >> 1)) > > #define PM_QOS_FLAG_NO_POWER_OFF (1 << 0) > #define PM_QOS_FLAG_REMOTE_WAKEUP (1 << 1) > >
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